package org.apache.http.impl;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.ConnectionClosedException;
import org.apache.http.Header;
import org.apache.http.HttpConnection;
import org.apache.http.HttpConnectionMetrics;
import org.apache.http.HttpEntity;
import org.apache.http.HttpException;
import org.apache.http.HttpInetConnection;
import org.apache.http.HttpMessage;
import org.apache.http.config.MessageConstraints;
import org.apache.http.entity.BasicHttpEntity;
import org.apache.http.entity.ContentLengthStrategy;
import org.apache.http.impl.entity.LaxContentLengthStrategy;
import org.apache.http.impl.entity.StrictContentLengthStrategy;
import org.apache.http.impl.io.ChunkedInputStream;
import org.apache.http.impl.io.ChunkedOutputStream;
import org.apache.http.impl.io.ContentLengthInputStream;
import org.apache.http.impl.io.ContentLengthOutputStream;
import org.apache.http.impl.io.EmptyInputStream;
import org.apache.http.impl.io.HttpTransportMetricsImpl;
import org.apache.http.impl.io.IdentityInputStream;
import org.apache.http.impl.io.IdentityOutputStream;
import org.apache.http.impl.io.SessionInputBufferImpl;
import org.apache.http.impl.io.SessionOutputBufferImpl;
import org.apache.http.io.SessionInputBuffer;
import org.apache.http.io.SessionOutputBuffer;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.Args;
import org.apache.http.util.NetUtils;

/**
 * This class serves as a base for all {@link HttpConnection} implementations and provides
 * functionality common to both client and server HTTP connections.
 *
 * @since 4.0
 */
public class BHttpConnectionBase implements HttpConnection, HttpInetConnection {

    private final Log log = LogFactory.getLog(getClass());

    private final SessionInputBufferImpl inbuffer;
    private final SessionOutputBufferImpl outbuffer;
    private final MessageConstraints messageConstraints;
    private final HttpConnectionMetricsImpl connMetrics;
    private final ContentLengthStrategy incomingContentStrategy;
    private final ContentLengthStrategy outgoingContentStrategy;
    private final AtomicReference<Socket> socketHolder;

    /**
     * Creates new instance of BHttpConnectionBase.
     *
     * @param buffersize buffer size. Must be a positive number.
     * @param fragmentSizeHint fragment size hint.
     * @param chardecoder decoder to be used for decoding HTTP protocol elements.
     *   If {@code null} simple type cast will be used for byte to char conversion.
     * @param charencoder encoder to be used for encoding HTTP protocol elements.
     *   If {@code null} simple type cast will be used for char to byte conversion.
     * @param messageConstraints Message constraints. If {@code null}
     *   {@link MessageConstraints#DEFAULT} will be used.
     * @param incomingContentStrategy incoming content length strategy. If {@code null}
     *   {@link LaxContentLengthStrategy#INSTANCE} will be used.
     * @param outgoingContentStrategy outgoing content length strategy. If {@code null}
     *   {@link StrictContentLengthStrategy#INSTANCE} will be used.
     */
    protected BHttpConnectionBase(final int buffersize, final int fragmentSizeHint, final CharsetDecoder chardecoder,
            final CharsetEncoder charencoder, final MessageConstraints messageConstraints,
            final ContentLengthStrategy incomingContentStrategy, final ContentLengthStrategy outgoingContentStrategy) {
        super();
        log.debug("Constructing...");
        Args.positive(buffersize, "Buffer size");
        final HttpTransportMetricsImpl inTransportMetrics = new HttpTransportMetricsImpl();
        final HttpTransportMetricsImpl outTransportMetrics = new HttpTransportMetricsImpl();
        this.inbuffer = new SessionInputBufferImpl(inTransportMetrics, buffersize, -1,
                messageConstraints != null ? messageConstraints : MessageConstraints.DEFAULT, chardecoder);
        this.outbuffer = new SessionOutputBufferImpl(outTransportMetrics, buffersize, fragmentSizeHint, charencoder);
        this.messageConstraints = messageConstraints;
        this.connMetrics = new HttpConnectionMetricsImpl(inTransportMetrics, outTransportMetrics);
        this.incomingContentStrategy =
                incomingContentStrategy != null ? incomingContentStrategy : LaxContentLengthStrategy.INSTANCE;
        this.outgoingContentStrategy =
                outgoingContentStrategy != null ? outgoingContentStrategy : StrictContentLengthStrategy.INSTANCE;
        this.socketHolder = new AtomicReference<>();
    }

    protected void ensureOpen() throws IOException {
        final Socket socket = this.socketHolder.get();
        if (socket == null) {
            throw new ConnectionClosedException("Connection is closed");
        }
        if (!this.inbuffer.isBound()) {
            this.inbuffer.bind(getSocketInputStream(socket));
        }
        if (!this.outbuffer.isBound()) {
            this.outbuffer.bind(getSocketOutputStream(socket));
        }
    }

    protected InputStream getSocketInputStream(final Socket socket) throws IOException {
        return socket.getInputStream();
    }

    protected OutputStream getSocketOutputStream(final Socket socket) throws IOException {
        return socket.getOutputStream();
    }

    /**
     * Binds this connection to the given {@link Socket}. This socket will be
     * used by the connection to send and receive data.
     * <p>
     * After this method's execution the connection status will be reported
     * as open and the {@link #isOpen()} will return {@code true}.
     *
     * @param socket the socket.
     * @throws IOException in case of an I/O error.
     */
    protected void bind(final Socket socket) throws IOException {
        Args.notNull(socket, "Socket");
        this.socketHolder.set(socket);
        this.inbuffer.bind(null);
        this.outbuffer.bind(null);
    }

    protected SessionInputBuffer getSessionInputBuffer() {
        return this.inbuffer;
    }

    protected SessionOutputBuffer getSessionOutputBuffer() {
        return this.outbuffer;
    }

    protected void doFlush() throws IOException {
        this.outbuffer.flush();
    }

    @Override
    public boolean isOpen() {
        return this.socketHolder.get() != null;
    }

    protected Socket getSocket() {
        return this.socketHolder.get();
    }

    protected OutputStream createOutputStream(final long len, final SessionOutputBuffer outbuffer) {
        if (len == ContentLengthStrategy.CHUNKED) {
            return new ChunkedOutputStream(2048, outbuffer);
        } else if (len == ContentLengthStrategy.IDENTITY) {
            return new IdentityOutputStream(outbuffer);
        } else {
            return new ContentLengthOutputStream(outbuffer, len);
        }
    }

    protected OutputStream prepareOutput(final HttpMessage message) throws HttpException {
        final long len = this.outgoingContentStrategy.determineLength(message);
        return createOutputStream(len, this.outbuffer);
    }

    protected InputStream createInputStream(final long len, final SessionInputBuffer inbuffer) {
        if (len == ContentLengthStrategy.CHUNKED) {
            return new ChunkedInputStream(inbuffer, this.messageConstraints);
        } else if (len == ContentLengthStrategy.IDENTITY) {
            return new IdentityInputStream(inbuffer);
        } else if (len == 0L) {
            return EmptyInputStream.INSTANCE;
        } else {
            return new ContentLengthInputStream(inbuffer, len);
        }
    }

    protected HttpEntity prepareInput(final HttpMessage message) throws HttpException {
        final BasicHttpEntity entity = new BasicHttpEntity();

        final long len = this.incomingContentStrategy.determineLength(message);
        final InputStream instream = createInputStream(len, this.inbuffer);
        if (len == ContentLengthStrategy.CHUNKED) {
            entity.setChunked(true);
            entity.setContentLength(-1);
            entity.setContent(instream);
        } else if (len == ContentLengthStrategy.IDENTITY) {
            entity.setChunked(false);
            entity.setContentLength(-1);
            entity.setContent(instream);
        } else {
            entity.setChunked(false);
            entity.setContentLength(len);
            entity.setContent(instream);
        }

        final Header contentTypeHeader = message.getFirstHeader(HTTP.CONTENT_TYPE);
        if (contentTypeHeader != null) {
            entity.setContentType(contentTypeHeader);
        }
        final Header contentEncodingHeader = message.getFirstHeader(HTTP.CONTENT_ENCODING);
        if (contentEncodingHeader != null) {
            entity.setContentEncoding(contentEncodingHeader);
        }
        return entity;
    }

    @Override
    public InetAddress getLocalAddress() {
        final Socket socket = this.socketHolder.get();
        return socket != null ? socket.getLocalAddress() : null;
    }

    @Override
    public int getLocalPort() {
        final Socket socket = this.socketHolder.get();
        return socket != null ? socket.getLocalPort() : -1;
    }

    @Override
    public InetAddress getRemoteAddress() {
        final Socket socket = this.socketHolder.get();
        return socket != null ? socket.getInetAddress() : null;
    }

    @Override
    public int getRemotePort() {
        final Socket socket = this.socketHolder.get();
        return socket != null ? socket.getPort() : -1;
    }

    @Override
    public void setSocketTimeout(final int timeout) {
        final Socket socket = this.socketHolder.get();
        if (socket != null) {
            try {
                socket.setSoTimeout(timeout);
            } catch (final SocketException ignore) {
                // It is not quite clear from the Sun's documentation if there are any
                // other legitimate cases for a socket exception to be thrown when setting
                // SO_TIMEOUT besides the socket being already closed
            }
        }
    }

    @Override
    public int getSocketTimeout() {
        final Socket socket = this.socketHolder.get();
        if (socket != null) {
            try {
                return socket.getSoTimeout();
            } catch (final SocketException ignore) {
                return -1;
            }
        } else {
            return -1;
        }
    }

    @Override
    public void shutdown() throws IOException {
        final Socket socket = this.socketHolder.getAndSet(null);
        if (socket != null) {
            // force abortive close (RST)
            try {
                socket.setSoLinger(true, 0);
            } catch (final IOException ex) {
                log.warn("Shutdown error", ex);
            } finally {
                socket.close();
            }
        }
    }

    @Override
    public void close() throws IOException {
        final Socket socket = this.socketHolder.getAndSet(null);
        if (socket != null) {
            try {
                this.inbuffer.clear();
                this.outbuffer.flush();
                try {
                    try {
                        socket.shutdownOutput();
                    } catch (final IOException ignore) {
                    }
                    try {
                        socket.shutdownInput();
                    } catch (final IOException ignore) {
                    }
                } catch (final UnsupportedOperationException ignore) {
                    // if one isn't supported, the other one isn't either
                }
            } finally {
                socket.close();
            }
        }
    }

    private int fillInputBuffer(final int timeout) throws IOException {
        final Socket socket = this.socketHolder.get();
        final int oldtimeout = socket.getSoTimeout();
        try {
            socket.setSoTimeout(timeout);
            return this.inbuffer.fillBuffer();
        } finally {
            socket.setSoTimeout(oldtimeout);
        }
    }

    protected boolean awaitInput(final int timeout) throws IOException {
        if (this.inbuffer.hasBufferedData()) {
            return true;
        }
        fillInputBuffer(timeout);
        return this.inbuffer.hasBufferedData();
    }

    @Override
    public boolean isStale() {
        if (!isOpen()) {
            return true;
        }
        try {
            final int bytesRead = fillInputBuffer(1);
            return bytesRead < 0;
        } catch (final SocketTimeoutException ex) {
            return false;
        } catch (final IOException ex) {
            return true;
        }
    }

    protected void incrementRequestCount() {
        this.connMetrics.incrementRequestCount();
    }

    protected void incrementResponseCount() {
        this.connMetrics.incrementResponseCount();
    }

    @Override
    public HttpConnectionMetrics getMetrics() {
        return this.connMetrics;
    }

    @Override
    public String toString() {
        final Socket socket = this.socketHolder.get();
        if (socket != null) {
            final StringBuilder buffer = new StringBuilder();
            final SocketAddress remoteAddress = socket.getRemoteSocketAddress();
            final SocketAddress localAddress = socket.getLocalSocketAddress();
            if (remoteAddress != null && localAddress != null) {
                NetUtils.formatAddress(buffer, localAddress);
                buffer.append("<->");
                NetUtils.formatAddress(buffer, remoteAddress);
            }
            return buffer.toString();
        } else {
            return "[Not bound]";
        }
    }

}
